Powder metal rocker arm

ABSTRACT

A powder metal rocker arm is provided. The rocker arm may be connected to a cylinder head of an engine to assist in transferring motion between engine components. The rocker arm includes a pivot aperture formed therein to facilitate pivoting of the rocker arm with respect to the cylinder head. The rocker arm is formed of a metal alloy powder. The metal alloy powder is compacted to form an intermediate member. Secondary features, such as apertures and other weight reducing features may be formed in the intermediate member. The intermediate member is then sintered to form the rocker arm.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit from U.S. Provisional Patent Application No. 61/198,726, entitled “Powder Metal Rocker Arm,” filed on Nov. 7, 2008, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

The present invention relates generally to rocker arms and methods of manufacturing rocker arms, more specifically, the present invention relates to powder metal rocker arms and manufacturing rocker arms from power metals.

BACKGROUND

Diesel and gasoline internal combustion engines typically include one or more pistons situated in cylinders. Engines generate motion by igniting a mixture of fuel and air in a cylinder, causing a piston to move within the cylinder. The fuel and air enters the cylinder through an intake valve located in the body of the cylinder. Exhaust generated by the ignition of the fuel and air mixture exits the cylinder through an exhaust valve located in the housing of the cylinder. An engine timely opens and closes such valves to facilitate the ignition of the fuel and air mixture and expulsion of the exhaust generated by the ignition.

A rocker arm may be situated in the engine to facilitate the opening and closing of the intake and exhaust valves. One end of a rocker arm is generally directly or indirectly coupled to a camshaft of the engine and the other end of the rocker arm is generally directly or indirectly in contact with a valve. The rocker arm may be arranged to pivot on a roller shaft or ball pivot such that as the camshaft moves one end of the rocker arm, the other end of the rocker arm opens or closes a valve.

Rocker arms for automobile and truck engines are typically manufactured from high-alloy steel castings or forgings. Rocker arms often include apertures passing through the body of the arm and features and contours on the surface of the arm. Such apertures and surface features may be formed by secondary, post-casting operations. For example, apertures are formed in the rocker arm by drilling through the high-alloy steel arm and surface features are formed by milling away material on the surface of the arm. The surfaces of cast or forged rocker arms typically need to be treated with secondary operations to improve rocker arm surface properties, such as wear resistance.

Secondary and post-casting operations are often complex, difficult and time consuming, which results in increases in cost, scrap rate, and manufacturing time. There exists a need in the art for rocker arms and methods for manufacturing rocker arms that lower time and cost of manufacturing arms and produce more precise and consistent rocker arms.

SUMMARY

A powder metal rocker arm is provided. The rocker arm includes a pivot aperture formed therein to allow the rocker arm to pivot with respect to a structure. The rocker arm may be connected to a cylinder head of an engine to assist in transferring motion between engine components.

In an embodiment, the rocker arm is formed of a metal alloy powder. The metal alloy powder is compacted to form an intermediate member. Secondary features, such as apertures and other weight reducing features may be formed in the intermediate member. The intermediate member is then sintered to form the rocker arm.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:

FIG. 1 illustrates a perspective view of a pair of rocker arms in accordance with the present invention and assembled with a cylinder head;

FIG. 2 illustrates a perspective view of the rocker arm of FIG. 2;

FIG. 3 illustrates a perspective view of the pair of rocker arms of FIG. 1 coupled to a rocker arm support by a pivot pin;

FIG. 4 illustrates a perspective view of another embodiment of a rocker arm in accordance with the present invention; and

FIG. 5 illustrates a perspective view of the rocker arm of FIG. 4.

FIG. 6 illustrates a flow chart of a method of forming a rocker arm.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for novel rocker arms and novel methods for manufacturing rocker arms from powder metals. The rocker arm may be manufactured from power metal such that the time and cost needed for secondary operations to manufacture the rocker arm are substantially reduced or eliminated.

A rocker arm 10 is provided. The rocker arm 10 may be assembled in an engine as illustrated in FIG. 1. It will be appreciated, however, that the rocker arm 10 may be assembled or used in conjunction with any device. Further, the engine or device may include a singular rocker arm 10 or a plurality of rocker arms 10. As shown in FIG. 1, a pair of rocker arms 10 are coupled to a cylinder head 12 of an engine.

The rocker arms 10 may be arranged to pivot with respect to a portion of the cylinder head 12. For example, the rocker arms 10 may be connected to a rocker arm support 14. The rocker arm support 14 may be mounted to the cylinder head 12. The rocker arm support 14 may include a pivot pin 16 to allow the rocker arms 10 to pivot with respect to the cylinder head 12. The pivot pin 16 may be integrally connected to the rocker arm support 14 or alternatively connected thereto. As shown in FIG. 1, the pivot pin 16 may extend through the rocker arm support. Each rocker arm 10 is coupled to an end of the pivot pin 16. The rocker arm 10 is rotatable with respect to the pivot pin 16 to allow the rocker arms 10 to pivot with respect to the cylinder head 12.

The rocker arms 10 may be connected to components of the cylinder block 12 to transfer motion from one component to another component. For example, a first end 18 of each rocker arm 10 may be attached to a rod 20. The rod 20 may be coupled to a camshaft (not shown). The rod 20 may be attached to the rocker arm such that the rocker arm 10 pivots in response to vertical movement of the rod 20. One or more apertures may be formed in the first end 18 of the rocker arm 10 to receive a portion of the rod 20. The apertures may be threaded to receive a threaded portion of the rod 20. Alternatively, the rod 20 may be connected to the rocker arm 10 by any means known in the art.

A second end 22 of each rocker arm 10 may contact a second component of the cylinder head 12, such as a valve stem 24. The second end 22 of the rocker arm 10 may include a touch pad 25. The touch pad 25 may contact the valve stem 24 to transfer the pivoting motion to the valve stem 24. For example, downward pivoting motion of the second end 22 may move the stem 24 downward to open the valve. The cylinder head may further include a spring 26 to bias the valve to a given position. For example, as the second end 22 of the rocker arm 10 moves upward, the spring 26 may bias the valve into the closed position.

In the arrangement illustrated in FIG. 1, it will be readily understood by those skilled in the art that as the camshaft moves the rod 20 up, the first end 18 of the rocker arm 10 moves up, and when the rod moves down, the first end 18 of the rocker arm 10 moves down. This arrangement causes the rocker arm 10 to pivot about the pivot pin 16 and the second end 22 of the arm 10 to move in an opposite direction of the first end 18 of the arm 10. Such movement opens and closes the intake valve 27 and exhaust valve 28.

The arrangement of the rocker arm 10, as described above, makes it necessary for the rocker arm 10 to include a number of apertures. For example, as seen in FIGS. 2 and 3, a pivot pin aperture 30 accommodates the placement of a pivot pin 16 though the body of the rocker arm 10. The pivot pin aperture 30 may extend through the body of the rocker arm 10 and be approximately centrally positioned on the body of the rocker arm 10. As previously referenced, a rod aperture 32 may be located the first end 18 of the arm 10 to accommodate attachment of the rod 20 to the rocker arm 10. In addition, a threaded hole 34 may be included in the first end 18 of the arm 10 to accommodate a setscrew 36 to further secure the rod 20 to the arm 10. The threaded hole 34 may be angled to allow the setscrew 36 to engage the rod 20 and hold the rod 20 in place. As aforementioned, the second end 22 of the rocker arm 10 includes a touch pad 25 to contact and move the valve stem 24.

In an embodiment best seen in FIGS. 4 and 5, a valve stem aperture 52 may be included in the second end 54 of the arm 50 to couple a stem 24 directly to the rocker arm 50. In addition to the apertures configured to facilitate attachment of the rocker arm 50 to the components of the cylinder head 12, the rocker arm 20 may include weight reducing surface features. Reduced weight of engine components is always desirable, particularly for engines designed for moving vehicles. Any reductions in weight increase the fuel efficiency of a vehicle and decrease the need to offset or balance the momentum of moving parts within an engine. As can be best seen in FIGS. 4 and 5, the rocker arm 50 may include recesses 56 in the body of the rocker arm 50 to reduce the weight of the rocker arm 50. Such recesses 56 are designed to reduce the weight of the arm 50 without jeopardizing the structural integrity or strength.

Typically, known rocker arm manufacturing methods form apertures and weight-reducing features through secondary operations after the casting or forging of a rough rocker arm. For example, apertures may be drilled into the body of the rocker arm 50, weight-reducing features may be milled into the surface of the rocker arm 50, and the body of the rocker arm 50 may be grinded to form or finalize the touch pad. Such secondary operations add time and cost to the manufacturing of a rocker arm. The present invention reduces or eliminates the cost and time needed for such secondary operations.

In an embodiment of the present invention, the rocker arm 10 or 50 is manufactured from a power metal, preferably a low-alloy powder iron. The powder metal is transformed to a rocker arm through a powder metallurgy process. As illustrated in FIG. 6, this process 60 includes the steps of mixing alloy powders 62, compacting the alloy powder in a die to form a compacted intermediate rocker arm 64, and sintering the intermediate rocker arm 68 to further bond the compacted powder and form a final rocker arm. An intermediate component, such as the intermediate rocker arm, is often referred to in the art as a green component.

The powder metallurgy process provides for several advantages over known cast or forged rocker arms. For example, the green rocker arm—i.e., after compacting and prior to sintering—has sufficient structural integrity to undergo modification through secondary operations. Thus, the process for forming a rocker arm 50 may include the step of forming features in the intermediate component 66. For example, features such as the pivot pin aperture 30, rod aperture 32, threaded aperture 36, and valve stem aperture 52 may all be drilled through the green rocker arm. Although the green rocker arm has sufficient structural integrity to undergo a drilling operation, it is substantially easier to drill through a green rocker arm than one that is produced by casting or forging of high-alloy metals. In additional examples, the touch pad 25 may be finalized by grinding the green rocker arm and the weight reduction features 56 may be finalized by milling the green rocker arm. Grinding and milling a green rocker arm is substantially easier than grinding or drilling a cast or forged rocker arm. Performing secondary operations on the rocker arm 10 and 50 prior to sintering reduces the cost and time needed to produce a rocker arm 10 and 50, when compared to known cast or forged rocker arms.

The nature of powder metallurgy processes, along with performing secondary operations prior to sintering, produces sintered rocker arms that are either the shape desired or have a net shape that is substantially closer to the final shape desired than the net shape of cast or forged rocker arms. When a sintered rocker arm is the desired shape, no additional secondary operations are needed, providing time and cost savings over known rocker arms. When the net shape of a sintered rocker arm needs additional secondary operations to reach a final desired shape, such operations are minor as compared to the operations needed to finalize cast or forged rocker arms, which provides time and cost savings. In addition, net shapes closer to the desired shape can reduce errors in secondary processing and reduce scrap rates.

Additional advantages include reduction in raw material costs and elimination or reduction of post-casting or post-forging surface treatment. Low-alloy powder is commonly less expensive than high-alloy casting or forging steel. In addition, cast or forged rocker arms normally require additional surface treatment to improve surface properties, such as wear resistance. Surfaces produced by compacting and sintering typically provide sufficient surface properties for a rocker arm.

Although the preferred embodiments of the present invention has been illustrated in the accompanying drawing and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter. 

1. A rocker arm comprising: a first end; a second end opposite said first end; a pivot aperture capable of receiving a pivot pin; wherein said rocker arm is comprised of a metal alloy powder that is compacted and sintered to form said rocker arm; and wherein at least one aperture is formed in said rocker arm prior to said rocker arm being sintered.
 2. The rocker arm of claim 1 further comprising a recessed portion formed in said rocker arm.
 3. The rocker arm of claim 2 wherein said recessed portion is formed in said rocker arm prior to said rocker arm being sintered.
 4. The rocker arm of claim 1 wherein said pivot aperture is formed in said rocker arm prior to said rocker arm being sintered.
 5. The rocker arm of claim 1 wherein said first end is connected to a rod coupled to a camshaft.
 6. The rocker arm of claim 1 further comprising a touch pad formed in said second end of said rocker arm.
 7. The rocker arm of claim 6 wherein said touch pad is formed in said rocker arm prior to said rocker arm being sintered.
 8. A rocker arm assembly comprising: a rocker arm support member; a pivot pin connected to said rocker arm support member a first rocker arm pivotally connected to said pivot pin; wherein said first rocker arm is comprised of a metal alloy powder that is compacted and sintered to form said first rocker arm; and wherein at least one secondary feature is formed in said first rocker arm prior to said first rocker arm being sintered.
 9. The rocker arm assembly of claim 8 wherein said secondary feature includes an aperture formed in said first rocker arm.
 10. The rocker arm assembly of claim 8 further comprising a second rocker arm connected to said rocker arm support member.
 11. The rocker arm assembly of claim 8 wherein said rocker arm support member is connected to a cylinder block of an engine.
 12. The rocker arm assembly of claim 11 wherein a first end of said first rocker arm is connected to a rod.
 13. The rocker arm assembly of claim 12 wherein a second end of said first rocker arm is connect to a valve stem.
 14. The rocker arm assembly of claim 12 wherein said first end of said first rocker arm includes an aperture configured to receive said rod.
 15. A method of forming a rocker arm comprising: compacting a metal alloy powder into a die to form an intermediate rocker arm member; forming a secondary feature in said intermediate rocker arm member; and sintering said intermediate rocker arm member to form a rocker arm.
 16. The method of claim 15 wherein said secondary feature includes a weight reducing feature formed in said intermediate rocker arm member.
 17. The method of claim 15 wherein said secondary feature includes an aperture formed in said intermediate rocker arm member.
 18. The method of claim 17 wherein said aperture is a pivot aperture formed in said intermediate rocker arm member.
 19. The method of claim 15 further comprising the step of mixing said alloy powder prior to compacting said alloy powder.
 20. The method of claim 15 further comprising the step of forming a touch pad in an end of said intermediate rocker member. 